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Simon Prosser is Senior Lecturer in Philosophy at the University of St Andrews. His main research interests are in the philosophy of mind and in metaphysics. He has published articles on temporal experience, inten-tionalism about conscious experience, indexical thoughts, the metaphys-ics of time, and emergent properties. He is currently adding the finishing touches to a monograph on the experience of time and change, and also writing a couple of papers on the individuation of concepts. In the future he plans to write more about the nature of conscious experience.

e d i t o r i a l n o t e

The following paper is a draft version that can only be cited or quoted with the author’s permission. The final paper will be published in Proceedings of the Aristotelian Society, Issue No. 3, Volume CXV (2015). Please visit the Society’s website for subscription information: www.aristoteliansociety.org.uk.

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w h y a r e i n d e x i c a l s e s s e n t i a l ?

s i m o n p r o s s e r

Despite recent challenges, it is commonly held that certain indexical terms such as ‘I’, ‘here’ and ‘now’ have a necessary or ‘essential’ role in certain kinds of action. I argue that this is correct, and I offer an expla-nation. A use of an indexical term of the kind in question connotes a mental representation of a specific relation between the thinking subject and the reference of the indexical. This mental representation has an epistemic feature that I call first-person redundancy. I show through a regress argument that a mental state of this kind is essential for common kinds of action, and perhaps for all actions.

i. introduction

FOLLOWING THE WORK of Castañeda (1966, 1967, 1969) and Perry (1977, 1979), many philosophers have held that there is something spe-cial or ‘essential’ about indexical terms, or about the thoughts that we express by using them. But what exactly does this special role consist in, and what is the argument for its being essential? In their recent book The Inessential Indexical (2014), Herman Cappelen and Josh Dever argue that the doctrine of the essential indexical has not been made adequately clear, and that there are no good arguments for any clear putative version of it.1 Consequently they argue that the common view that indexicality and the first-person perspective play an important and deep role in a variety of philosophical issues is a myth.

I do not agree; I believe that there is a clear and important distinction to be made between a first-person perspective and a third-person perspec-tive, that the doctrine of the essential indexical can be made clear, and that the doctrine can be defended using a simple regress argument. I shall ex-plain and defend that view in what follows. But I do agree with Cappelen and Dever that existing attempts to defend the doctrine are not adequately

1 See also Magidor forthcoming for similar views, and Millikan 1990 for an earlier chal-lenge. In fact I agree with much of what these authors say; for example, I do not think that it is indexicality per se that is essential, or that the phenomenon at issue involves a special category of de se content.

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simon prosser why are indexicals essential?

clear, and that the source of the essentiality of indexicals has frequently been misidentified. I agree, for example, that the essential nature of index-icals does not derive from any special kind of content, or from indexicality per se. Although I shall note some connections with their work, however, this paper is not primarily a reply to Cappelen and Dever. Instead, I shall focus on giving a positive account of what is essential about indexicals. I shall argue that each member of a certain class of indexicals is associated with a mental representation of a special kind that is essential for cer-tain kinds of action. (By ‘mental representation’ I just mean any kind of mental state that can usefully be interpreted as having a representational content. My use of this expression implies no commitment to any stronger doctrine.2) The representational states in question have a unique epistemo-logical feature that arises from the fact that each one represents a relation in which the thinking subject is one of the relata.

ii. the doctrine of the essential indexical

I shall start by clarifying the view that I wish to defend. The most com-mon view about the essentiality of indexicals is that without the kind of thought normally expressed using an indexical, it is not possible to act. It seems clear enough that indexical language cannot be essential for action; we can perfectly well imagine a language with no indexical terms, but it is not plausible that its speakers would be unable to act. So the claim must concern mental states rather than language. I shall claim that the presence of an essential mental state is indeed indicated by the use of an indexical term, but this does not entail that the thought itself is somehow indexical. In fact, in my view, the mental states that concern us are not indexical in any important way. A fortiori it is not indexicality per se that explains the essential nature of indexicals. Thus when I speak of indexicals being essential I mean only that certain mental states associated with the use of certain indexicals, which I shall call egocentric mental states, are essential for action. I shall not claim that egocentric mental states are, themselves, indexical.

Some further restrictions are needed. I shall restrict my claim to what I shall call the egocentric indexicals; indexicals such as ‘I’, ‘here’ and ‘now’

2 Throughout this paper I assume without argument that mental states, including ex-periential states, have representational contents. This is a common assumption, but is rejected for experiences by naïve realists about perception. I suspect that a naïve realist could accept much of what I say here, however, by replacing talk of experiential repre-sentation with talk of the content of experience (construed as whatever the experience is an experience of). The crucial notion of first-person redundancy, described below, can be understood in purely epistemological terms, so it is not clear that the notion of represen-tation is essential to it.

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simon prosser draft paperwhy are indexicals essential?

which, I shall argue, are associated with mental states that capture the subject’s perspective. Consider the spatially non-egocentric indexical term ‘hereHC’, which refers to the present location of Herman Cappelen. I do not think that advocates of essential indexicality have intended to claim that indexicals such as ‘hereHC’ are essential in the relevant sense (except insofar as they involve an implicit ‘now’), and neither shall I. Neither shall I claim that pure demonstratives such as ‘that’ are essential, or at least not in the same way.3 The reason for the restriction, and its scope, will become clearer in due course.

Perhaps not all possible actions require indexicals; for example, per-haps there could be God-like creatures who lived outside space, and per-haps time, who acted just by imagining the world to be in a certain state. This is a subtle matter, and will be more easily addressed once certain other notions have been introduced. I shall return to it below. In any case I shall restrict myself to the claim that there is a class of actions, CA, which humans commonly perform, for which egocentric indexicals are essential. I leave it open, for now, whether there are possible actions not included in CA. Consequently I shall be arguing for a claim of the following form:

The Doctrine of the Essential IndexicalThere is a class of actions, CA, such that no action in CA can be performed by an agent who lacks the relevant egocentric mental state, the presence of which is normally indicated by the use of an egocentric indexical.

The reason for putting this in terms of mental states whose presence is in-dicated, rather than expressed, by the use of an indexical will be explained in the next section.

iii. the connotation principle

Let ‘L’ be an egocentric indexical term. Consider a subject, S, who ex-presses a thought by saying something of the form ‘L is F’, where ‘L’ refers to a place, person or time, l. Assuming S’s utterance to be sincere, we can conclude that S believes, of l, that it is F. But in choosing to use the indexi-cal term ‘L’, S manifests further beliefs. For example, given that uses of ‘now’ are governed by the rule that a token of ‘now’ refers to the time at

3 John Campbell (2003) suggests that demonstrative thoughts have an essential role be-cause they involve selecting a target object toward which an action can be directed. I do not want to rule out that there may be some such role. But I do not think this explains the essential role of indexicals such as ‘I’, ‘here’ and ‘now’. See below.

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which the token is uttered, if S uses ‘now’ to refer to a time t then the fact that S uses ‘now’ indicates that S believes that t is the time at which ‘now’ was uttered. Similarly, a use of ‘here’, referring to location l, indicates that S believes that l is the place in which ‘here’ was uttered, and a use of ‘I’, referring to person S, indicates that S believes that S is the person who uttered ‘I’. Let us call beliefs of this kind indicated linguistic beliefs, thus distinguishing them from the beliefs expressed by the utterances.

Notoriously, however, the linguistic belief indicated by the use of an egocentric indexical does not fully account for the psychological signifi-cance of the indexical. The point was perhaps first noticed by Arthur Prior (1959) who observed that while it makes sense to say ‘thank goodness that’s over’ about a traumatic event, it would make no sense to thank goodness for the fact that completion of the traumatic event occurred at an earlier time than the time of the utterance; for that would have been just as true before the traumatic event as after.4 Prior drew controversial conclusions about the metaphysics of time, but in fact the ‘thank good-ness’ case has close parallels with other indexicals. For example, it makes sense for me to thank goodness that the ferocious tiger is not here, and that it will not attack me, but without supplementary premises it does not makes sense to thank goodness that the ferocious tiger is not at the loca-tion of some specified utterance, or will not attack the speaker of some specified utterance. François Recanati (1993, pp. 69-72) has argued that we must thus distinguish what he calls linguistic and psychological modes of presentation; the former embody the rule that determines the reference of a token indexical, but only the latter capture the psychological role as-sociated with egocentric indexicals.

The need for this distinction arises because what ultimately matters for the subject’s actions is a relation between the reference and the thinking subject, not a relation between the reference and a linguistic token. The latter is significant only insofar as it entails the former. I suggest, then, that a use of an egocentric indexical manifests a further belief – one that the subject would often have even in the absence of an utterance - which I shall call the indicated egocentric belief. This concerns a relation between the reference and the thinking subject. In the case of spatial indexicals this is highly plausible. If S refers to a place l using the word ‘here’ then normally S believes that l is where S is located. l is, as S might put it, here-abouts. Suppose that Smith, while located at l, believes ‘there is danger here’ while Jones, located elsewhere, believes ‘there is danger there’, where Jones’s token of ‘there’ also refers to l. Then Smith and Jones both believe

4 For my own positive account of the ‘thank goodness’ case, see Prosser forthcoming a: chapter 3.

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that there is danger at l.5 In addition, however, Smith also believes that l is where Smith is located. Jones might also happen to believe that l is where Smith is located, but this belief is not manifested by Jones’s use of ‘there’. Moreover, as I shall explain below, even if Smith and Jones both believe that l is where Smith is located, they do not believe this in the same way. Smith believes it in a way that is essential for certain kinds of action; Jones does not.

The equivalent claim about ‘now’ is that when Smith believes ‘there is danger now’, Smith believes, of some time t, that there is danger at t, but Smith’s use of ‘now’ indicates that Smith also believes that t is pres-ent. This much, I think, is hard to deny; one could not coherently make an ordinary, sincere use of ‘now’ while denying that the time in question was present. The temporal case is more complicated than the spatial case, however, because there is a debate in metaphysics about whether present-ness is a primitive property of times (or perhaps events). If so, then insofar as ‘now’ thoughts have a special significance for action, this is because it makes a difference for one’s actions whether or not a certain time or event is present. Those of us who accept the B-theory of time, however, and who thus deny that times have properties like pastness, presentness or futurity, must instead regard pastness, presentness and futurity as relations. There is some debate concerning the relata, given that persons exist at more than one time. However there is much to be said for a theory according to which presentness is a relation between a time or event, and a person-stage.6

It might seem less clear that there is any comparable relation associ-ated with ‘I’, but in fact there is such a relation. Consider Smith and Jones, sitting facing one another, and both wanting to raise Smith’s arm. Smith and Jones can both raise Smith’s arm. But they must do this in different ways, and this is because of their different relations to Smith. Smith is identical with Smith; Jones is not. But Smith stands in more relations to Smith than just identity. In particular, Smith stands in a relation to Smith such that Smith can raise Smith’s arm at will. Jones does not stand in that relation to Smith. If Jones wishes to raise Smith’s arm then Jones must do so by some other means, such as reaching out with Jones’s own arm to lift Smith’s arm. Smith is also the recipient of perceptual information acquired through Smith’s sensory organs. Jones is not, and thus does not stand in that relation to Smith either. Let us gather all these relations together as a single relation, and call this the i-relation. Smith stands in the i-relation to

5 For present purposes we can set aside the question of whether Smith and Jones both think of l under the same mode of presentation. For an argument that they can do so, however, see Prosser forthcoming b.6 For a lengthier defence of this view, see Prosser forthcoming a: chapter 3.

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Smith, but not to Jones. Jones stands in the i-relation to Jones, but not to Smith. Or perhaps there are slightly different i-relations for different peo-ple, reflecting their slightly different capacities in relation to themselves. I shall leave this open, but for simplicity I shall speak as though there is a single i-relation. I suggest that a person, S, who uses the word ‘I’, nor-mally believes that S stands in the i-relation to S. In fact any self-conscious subject does so. But, as I shall explain below, although in principle anyone could believe that S stands in the i-relation to S, there is a special way of believing it that is only available to S.

The i-relation is a member of a more general class of relations. These are relations between a thinking subject, S, and an object, place, time or person, o, where that relation determines certain possibilities for interac-tion between S and o. These relations bear similarities to those that J. J. Gibson (1979) called affordances, and to reflect this I shall sometimes call them affordance relations. I wish to stress, however, that I am not thereby committed to any view of Gibson’s and, in particular, not committed to his anti-representationalism. I am merely discussing similar relations. I should also stress that affordance relations, as I construe them, are subject-en-vironment relations that determine which types of subject-environment interactions are possible. They should not be thought of as the sets of ac-tions thus determined.

The psychologically important relations associated with ‘here’ and ‘now’ are also most plausibly thought of as affordance relations, rather than spatial or temporal relations. For example, the ways in which S can act on o might depend on whether o is near. But arguably the ‘near’ rela-tion that is relevant to S’s actions is the relation that is common between a small creature one metre from an object, a large creature ten metres from an object, and a creature that lives in a computer-generated virtual environment and stands in a functionally equivalent, but non-spatial, rela-tion to a virtual object. A similar claim can be made in the temporal case.7 If, however, this is incorrect, and the relations in question are spatial or temporal, this should not affect the argument that follows. I shall hence-forth refer to these relations neutrally as subject-environment relations, or s-e relations for short. S-e relations include only relations that determine possibilities for subject-environment interactions; they do not include all relations between a subject and an environment.

We can summarise the claims of this section in the following principle. The word ‘object’ is used here to mean a place, time, person or physical

7 Arguments for thinking that the psychologically salient relations in spatial experience and thought are affordance relations are given in Prosser 2011; and the equivalent claim for temporal experience and thought is defended in Prosser forthcoming a: chapter 4.

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object, and the word ‘connotation’ is used in the ordinary, non-technical sense:

The Connotation PrincipleWhen a subject, S, uses an egocentric indexical term ‘L’ in referring to an object o, S’s use of ‘L’ indicates that S believes that S stands in an s-e relation to o. Different indexicals connote different s-e relations.

Note that ‘pure’ demonstratives such as ‘that’ do not connote s-e rela-tions, and consequently I am not claiming that ‘that’ is an essential indexi-cal. It is true that when S uses ‘that’ in referring to a perceived object, S is often aware of an s-e relation to the object due to the object’s experienced location in egocentric space. But this is not always the case; one can talk, and arguably think, about a person or object that one hears, despite being unable to tell which direction the sound is coming from, and in such cases one can express one’s thought using ‘that’.

I think that the connotation principle is highly plausible, but in any case there are good independent reasons to accept it. For example, it offers a very simple account of the systematic differences in behaviour associated with different indexicals. One stands at a distance from location l and one thinks ‘it rains constantly there’. Then one travels to l, thinking about it continuously, and one expresses a retained belief using the words ‘it rains constantly here’. All else being equal, when one uses ‘here’ one opens one’s umbrella, but when one uses ‘there’, one does not. This difference in actions suggests a difference in one’s beliefs. Given the connotation prin-ciple, there is an obvious explanation: although one retains the belief ‘it rains constantly at l’, it is only when one uses ‘here’ that one also believes that l is hereabouts. It is this latter belief that leads one to open one’s um-brella. It would be hard to account for both the retention of a belief and the difference in behaviour in any other way.8

Perhaps the suggestion that a user of an indexical term believes that she or he stands in the relevant s-e relation will be thought too strong. This may depend on what one builds into the notion of belief. I am as-

8 I give a full defence of this line of thought in Prosser 2005, and discuss its analogue for the case of thoughts shared between different speakers who are in different contexts in Prosser forthcoming b. I also discuss the significance of the connotation principle (though not under that name) for the phenomenon of immunity to error through misidentifica-tion in Prosser 2012. In my opinion, much philosophical confusion has resulted from attempts to account for indexical thoughts in terms of special, unstructured singular modes of presentation with unique inferential roles, instead of recognising that different indexicals are associated with different s-e relational beliefs.

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suming only a very liberal notion of belief such that, roughly speaking, a creature counts as believing that p just if assuming so helps us make better sense of the creature’s systematic behaviour.9 There are stronger notions of belief, such as those that take belief to be a relation to a structured propo-sition composed of concepts. But, as I see it, this is a mere terminological issue; nothing in the explanation of the essential indexical that I am about to offer depends on whether the egocentric mental states in question are properly called beliefs.

iv. knowing how one can act

The Connotation Principle does not, in itself, explain what makes indexi-cals essential. Consider David Lewis’s (1979) famous example of the two gods, who know every proposition true of their world, and thus know exactly which possible world they live in. The gods do not, however, know who or where they are in that world; their knowledge is only expressible in non-indexical form. If a subject, S, stands in an s-e relation, R, to an object, o, then the gods know this, no matter who S is. So if, as Lewis sug-gests, the two gods are missing something that would enable them to act in the world, what is missing cannot be knowledge of the form ‘S stands in relation R to o’, for they already know all such propositions.

Lewis’s gods do indeed lack something essential for action. I shall ar-gue in subsequent sections that what they lack is a special kind of access to their s-e relations, a particular kind of epistemic perspective on one or more propositions of the form ‘S stands in relation R to o’. Only S can stand in that perspective to that content. First, however, let us consider why mental representations of s-e relations should be thought to play an important role in action at all.

Any creature that uses its body to perform actions on its immediate environment must be sensitive to its relations to its environment; oth-erwise it would not be able to act in the right way. It might, however, be questioned whether s-e relations have an important role in the psy-chology of the agent. It might be suggested, for example, that such states play their role at a sub-personal level. This might seem plausible if one does not notice that explanations can differ in how fine-grained they are. Consider, for example: I believed that I had been invited to give a talk in London, I desired to give the talk, so I travelled from St Andrews, where I live, to London. That is a perfectly good rationalising explanation of my travelling from St Andrews to London. But of course during my journey a multitude of finer-grained beliefs and desires came into play, without

9 For this kind of view see Dennett 1987, 1991.

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which I could not have made the journey. So there is a danger of moving too quickly from the possibility of explaining someone’s action without mentioning any representations of s-e relations to the conclusion that no representations of s-e relations played any role in the action.10

There may well be certain kinds of sub-personal representations that play a role in determining fine-grained bodily movements, including habit-ual actions and other relatively ‘automatic’ movements. When one reaches out to pick up an object, one typically does not consciously think about how to arrange one’s fingers in order to grip the object; there is a sense in which this happens automatically. But it would be far too quick to con-clude from such cases that conscious thoughts about s-e relations have no role to play in one’s actions. An action is something that one intends to perform. When one intends to pick up an object, one typically does not intend to shape one’s grip in a particular way. But often one’s intentions do place constraints on how the action is performed, and this usually requires awareness of certain s-e relations. One’s beliefs and experiences concerning s-e relations allow one to make judgments about what kinds of actions one can perform. Can I reach that object with my left hand, or should I use my right hand? Do I need to bend down to get through that doorway? Can I get to the tennis ball before it crosses the line? Should I try to move in such a way as to receive the ball on my stronger side? The fact that such deliberations are possible shows that mental representations of s-e relations have a role in the production of many intentional actions.11

If one knows the result that one wishes to achieve, but one is entirely unaware of one’s s-e relations, then with some luck one might be able to achieve the desired result by thrashing around at random. Even Lewis’s two gods could do this. But action is not normally like this; one usually intends to move in more or less the way that one actually moves, at least at a coarse-grained level. But note that even if, contrary to what I have suggested, representations of s-e relations could only perform their func-tion at a sub-personal level, the arguments of the next two sections would still show that such representations were essential for an important class of actions.

10 See for example Cappelen and Dever 2014, ch. 3, where an emphasis is placed on the notion of explanation.11 If the ‘two streams’ hypothesis of Goodale and Milner 1992 is correct then many fine-grained bodily movements are controlled by a processing stream quite separate from that which leads to conscious experience. But that is consistent with the possibility that the relational content of conscious experience makes it possible to know which actions one can perform and how one can perform them, and to form the intention to perform an action in a (fairly) specific way. This provides a partial response to Campbell’s (2003) claim that conscious experience only enables the subject to select a target for action and has no role to play in guiding the action.

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Are mental representations of s-e relations essential to all kinds of action performed by all possible agents? It is tempting to think not, on the grounds that there could be a god-like creature who acted just by specifying the desired state of affairs. We must distinguish some different cases. In the extreme case, perhaps there could be a god-like creature who did not exist in space or time, but could create the entire spatiotemporal world. But this is clearly not how human beings act, and perhaps should not be described as an action at all. Consider instead a god-like creature located in time, but not in space. Perhaps this god could be equipped with a complete linguistic representation of the world, including a name for every particular. This god could act by stating a complete description of how the world was to be at some future time, or perhaps just a description of whatever would change, much as one might specify a move in a chess game. We can also consider a god just like the previous one, but located in space as well as time. From the god’s point of view everything would be the same; the desired outcome would be specified in the same way, but sometimes the god would move in such a way as to produce the desired outcome. But this movement would not be performed consciously or de-liberately; from the god’s point of view, it would just happen.

Perhaps such god-like actions are possible. If so, then the doctrine of the essential indexical must be restricted such that the relevant class of actions, CA, does not include them. This would not undermine the claims that I wish to make, provided human action is not generally god-like. But, despite its initial plausibility, the notion of god-like action requires careful scrutiny. As noted above, one does not act unless one intends to act. Some-thing that happens merely as an unintended by-product of one’s mental activity is not an action. So it would not be action if all that happened was that the god envisaged or described a state of affairs, and forces beyond the knowledge or control of the god made that state of affairs obtain. For it to be an action the god must intend that state of affairs to obtain. Moreover, suppose the god lived in a very simple world containing just two objects, A and B, and intended the final state of affairs to be that A had moved closer to B. It would not be sufficient merely to imagine A and B closer together, and intend that this be the case. For that would leave it indeterminate whether it was A or B that was to be moved. So the god must intend to move A, rather than B. How would the god achieve this? Presumably through some sort of act of will (for want of a better way of putting it), directed at A rather than B. A god capable of selectively mov-ing just A or B would require the ability to direct such acts of will at one or the other object by choice. In order for the action to be deliberate, the god must know how to do this. But this suggests an awareness of stand-ing in different relations – non-spatiotemporal affordance relations of a certain kind – to A and B. The god might think: ‘A is such that it can be

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moved by doing this [imagines the relevant act of will] whereas B is such that it can be moved it by doing that [imagines a different act of will]’. This suggests that even a god would have to stand in different s-e relations to different objects in order to be able to act on them, and must have some kind of awareness, and thus some kind of mental representation, of those relations. If this is correct then there is no such thing as god-like action after all.12

In any case, regardless of whether god-like action is really possible, most ordinary human actions require representations of s-e relations. Without them, one would not know what one was capable of doing, or how to do it. This is the situation in which Lewis’s two gods find them-selves. They are aware of the current state of the world, and perhaps they know how they would like it to be, but they do not know how to bring this about. Let us call them god#1 and god#2. Suppose both gods desired that god#1’s arm raise. Because they stood in different relations to god#1, they would have to act in different ways to produce that result. God#1 could achieve the result by producing a motor output, contracting the relevant muscles and thereby causing the arm to raise. God#2 could pro-duce the result by moving god#2’s body in such a way as to raise god#1’s arm. Both gods know all of this, of course. Their problem is that, despite all their knowledge, they do not know how to act to produce the desired result. In the next two sections I explain what is missing.

v. first-person redundancy

Imagine a creature, C, living in a one-dimensional world consisting of a single line of space. The creature eats Os, which are objects of a certain kind that it finds along the line. C captures these objects by performing an action (extending its tongue, perhaps) just when an O is one metre away from it. Now, if any creature other than C wished to be able to react just when an O was one metre from C, it would normally need to detect two things: the location of the O, and the location of C. In principle there could of course be a creature with direct conscious awareness of the dis-tance between C and O due to having some special kind of direct access to that parameter (by literally seeing the world through C’s eyes, for ex-ample). But this would not be the normal case for creatures that perceived their environments in anything like the way that humans do.

C stands in a special epistemic relation to the distance between C and an O, however. All that C needs to do is to react when an O is one metre

12 Much the same line of argument would apply to action through telekinesis, mentioned by Millikan (1990, pp. 727) in her argument against essential indexicality.

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away. C might, for example, have a form of echolocation that caused C to react just when the return time for the echoes dropped to a certain level, indicating that an O was one metre away. In other words, C need only be sensitive to one distance parameter, instead of having to compute that parameter from the two parameters that specify the positions of C and the O. This single parameter would also be sufficient for C to control C’s ac-tions. Suppose, for example, that C had the capacity to eat Os at different distances by adjusting C’s actions in some way (perhaps C could extend its tongue different distances, for example). Again, only a single parameter would be required.

Suppose that C did in fact perceive C due to a reflection or refraction of some kind. This would make no difference to C’s interactions with Os. C would still need to respond to only one parameter, represented directly in experience, in order to interact with the Os. Any experiential represen-tation of C would therefore be redundant in C’s interactions with Os. This would be equally true of C’s beliefs. C might believe that there was an O at a certain distance, and react accordingly, even if C did not perceive the O. Again, only one parameter need be involved in this. C would need only to believe that the O was near; C would not need to believe that the O was near to C. Since C’s representations of C would be redundant, I shall say that C’s representation of the spatial relation between C and an O is first-person redundant.

It seems clear that humans make frequent use of the same kind of epis-temological short cut, which is possible just when the subject is one of the relata in an s-e relation. When I reach out to touch an object, I need only perceive that the object is nearby and to the left (say); I do not need to compare the location or orientation of the object with my own. The point generalises to other relations; whenever S stands in an s-e relation, S can in principle be in an epistemically privileged position with respect to the obtaining of that relation, and will be able to perform appropriate actions without needing to be sensitive to as many parameters as someone else who wished to be sensitive to the obtaining of the same relation. So there are many human actions that depend on representational states that are first-person redundant.

We should be careful not to conflate the notion of first-person redun-dancy with the claim that the thinking or perceiving subject can be an unarticulated constituent of the thought or experience. The notion of an unarticulated constituent was made prominent by John Perry (1986), who described a fictional place called Z-land in which the inhabitants spend their entire lives in the same place. They do not even think about other places. Consequently they have no use for words like ‘here’. Instead of

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saying ‘it is raining here now’, they just say ‘it is raining now’. Perry sug-gests that the same could be true for the Z-landers’ thoughts. They speak, and even think, as though rain were a one-place predicate of times. Yet when they say, or think, that it is raining now, this is true if and only if it is raining in Z-land now. Z-land is thus an unarticulated constituent of the proposition expressed. Similarly, if a Z-lander had made the same claim at time t in another place, l, the truth condition would have been that it is raining in l at time t. In principle the idea can also be applied to cases in which it is the thinking subject that is unarticulated. I may, for example, say or think that object o is near to me by saying, or thinking, ‘o is near’. If I am person S, then what I say is true if and only if o is near to S. Others have subsequently made similar claims.13

It is easy enough to make sense of the idea of an unarticulated con-stituent in language; it arises whenever a syntactically n-place predicate is used in dealing with what is in fact an n+1-place relation. But can we say the same about the contents of thoughts and experiences? This seems intuitively plausible. An object can look near or to the left without being explicitly represented in vision as near or to the left of me. I, the perceiving subject, do not have to appear in the content of the experience. An object can look nearby without my being able to see myself, and therefore with-out my being explicitly represented in the content of my visual experience.

But experiential content does not have a linguistic form, so the presence of an unarticulated constituent cannot be understood as it is for language, by comparing the number of syntactic argument places with the number of argument places in the truth condition. Perhaps the problem could be solved by appeal to phenomenology; an object is not an articulated con-stituent of the content of an experience unless there is an element of the phenomenology that represents it. This leaves it unclear what we should say about cases of amodal completion, however, in which an occluded part of an object is arguably present in the experience. Consider the com-mon example of a cat seen behind railings; one’s visual experience seems to include the whole cat, yet only parts of the cat are visible. Perhaps it might be argued that the phenomenology of the experience includes the whole cat, and merely fails to represent the surface properties of those parts of the cat that are not visible. So perhaps a comparable claim could be made about the presence of the subject in experience.14

13 In particular, John Campbell (1994, 2002) and Sydney Shoemaker (1994) have both suggested that the egocentric content of experience is of this ‘monadic’ form.14 John Schwenkler (2014) makes precisely this claim. Schwenkler argues that the subject must, in fact, be represented in experience, or there could be no phenomenological dif-ference between one’s own motion and the motion of objects around one. Although I think there may be a reply to Schwenkler’s argument, for present purposes it is sufficient

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In any case, there is no straightforward reason to think that first-per-son redundancy would require there to be an unarticulated subject. First-person redundancy is an epistemic notion, whereas the notion that the subject is an unarticulated constituent is a semantic notion. They are thus entirely different notions.

vi. why first-person redundancy is essential

I argued in section IV that in order to act on object o (where ‘object’ is construed broadly) one must be aware of one’s s-e relations to o; other-wise, one would not know which actions one could perform, or how to go about performing them. But this cannot be the whole story, given that Lewis’s two gods know every true proposition expressed in non-indexical form, and thus know every proposition of the form ‘S stands in relation R to o’. Knowing how to act is not the same as knowing how S can act, even if I am in fact S. Ordinary knowledge that S stands in an s-e relation R to o gives me the right information, but it does not give it to me in the right form. Instead, for information about my s-e relations to enable me to act, their representation must be first-person redundant.15

This can be shown by a regress argument. Suppose that I am S and I stand in s-e relation R to o, and I wish to perform an action on o that depends on my relation to it. My mental representation of this relational state will typically be first-person redundant. For example, from my point of view, o might appear nearby and to the left. This might be because I see it as nearby and to the left, or it might be because I merely believe this to be the case (perhaps it is dark, or o is invisible). This representational state gives me what I need in order to perform the action. But the equiva-lent non-redundant state (i.e. a state which is not first-person redundant) would not.

Consider a non-redundant mental state with a content of the form: ‘S stands in R to o’. Suppose first that S were not me, and that I wanted to make S act on o. A representation of that kind might help me to make S move in the desired way relative to o, but only if I knew how to act upon S in that way. Given the arguments of the preceding sections, knowing how

to note that first-person redundancy does not require an unarticulated subject. It is of course possible that Schwenkler is right, and that those who have thought otherwise were implicitly conflating first-person redundancy with the unarticulated subject. However I am also open to the possibility that there is a necessary, and perhaps explanatory connec-tion between the two phenomena.15 It is implicit in the preceding sentences that the notion of first-person redundancy may also hold the key to understanding the distinction between knowing how and knowing that. I intend to elaborate on this in future work.

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to act on S would require me to have a mental representation of an s-e relation between myself and S. If in fact I were S then the relevant relations would be the s-e relations that I stand in to myself – the kind of relation that I called an i-relation above. But if my mental representation of the i-relation is not first-person redundant then a mental representation of a further s-e relation will be needed. A regress threatens.16

It will help to write this more formally in a notation that captures both the semantic content of a mental state and its epistemic status. Let ‘R(S, o)’ stand for the content ‘S stands in relation R to o’, where the represen-tation of S is non-redundant. Let ‘R({S}, o)’ be a first-person redundant representation with the same semantic content. Thus, if I am S, then in the ordinary case in which I act on o I have a first-person redundant mental representation of the form R1({S}, o). But suppose instead that this repre-sentation were non-redundant, i.e. R1(S, o). Then I would be in a similar situation to anyone else who wanted to make S act in relation to o; I would need to do so by acting on S. Given the arguments above, in order to act on S I would need a mental representation of some appropriate rela-tion that I stood in to S. To act in this way would be rather unnatural – I do not normally act on other objects by first acting on myself, to make myself move in the right way relative to the object. But perhaps there are cases in which this becomes necessary.17

Now, given that I am S, the mental representation required for my ac-tion upon myself (and thus to act indirectly upon o) would either be of the form R2({S}, S) or of the form R2(S, S). But if it were the latter then I would be in a similar position to anyone else who wanted to make S act upon S. I would thus need a further representation of another s-e relation between myself and S; either R3({S}, S) or R3(S, S). Clearly the iterations will con-tinue until a first-person redundant representation is reached. I therefore conclude that no action (or at least no action in CA) is possible without a mental representation that is first-person redundant. The regress is illus-trated by figure 1, in which the arrows point from the agent toward the object of the action, and the regress here halts at the third stage.

16 Other philosophers have suggested that there was some kind of infinite regress associ-ated with the first-person. See for example Ryle 1949, pp. 186-9. See also Merleau-Ponty 1962, pp. 104-5. I think the underlying ideas are related, and shed much light on the ‘elusiveness’ of the self, as noted by Hume.17 The case of Ian Waterman (described in Cole 1995) may illustrate something of the difficulty in acting on another object by deliberately acting on oneself. At the age of 19 Waterman lost all sense of touch and proprioception from the neck down, but was not paralysed. He was able to compensate to some degree, but with great difficulty, by us-ing vision to tell him the configuration of his limbs. Perhaps Waterman is an example of someone who lacks the usual awareness of certain i-relations.

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Figure 1

vii. why indexicals?

There is nothing in the account that I have put forward to suggest that indexicality per se makes indexicals essential.18 But consider again the no-tion of the unarticulated subject, discussed above. Suppose that it were shown that in fact first-person redundancy and the unarticulated subject entailed one another. Would an unarticulated subject involve a kind of indexicality, suggesting that indexicality itself is essential for action after all? A positive reply might be motivated by the thought that experiences and perhaps other mental states have incomplete contents of the form ‘_ stands in R to o’, and that when these contents are entertained by different subjects they form different complete propositions. Thus when Smith and Jones are in identical internal states, Smith’s state determines the content ‘Smith stands in R to o’, while Jones’s state determines the content ‘Jones stands in R to o’.

This, however, is not indexicality. Smith and Jones have in common that their mental states represent each of them as being an x such that x stands in R to o. But an indexical is an element of the vehicle whose semantic value varies systematically with context. Nothing that has been said suggests that there is any such indexical element involved in the rep-resentations of Smith or Jones’s relations to o. Perhaps this error is made more tempting by a common conflation of egocentricity with indexicality. Words like ‘left’, ‘right’, ‘up’, ‘down’, and ‘near’ are egocentric in that they capture relations between a person and the person’s environment. But un-like ‘I’, ‘here’ and ‘now’, they are not indexicals. Their semantic values do not vary systematically with context according to token-reflexive rules.

Lewis (1979) argued that essential indexical content was de se content, which he argued could be characterised in terms of sets of centred worlds, or in terms of properties that are self-ascribed. Cappelen and Dever (2014,

18 The next two paragraphs are influenced by Cappelen and Dever 2014, ch. 8.

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ch. 5) make a convincing case that any centred worlds content can be expressed as a structured proposition, and therefore that there is nothing about centred worlds content that could explain essential indexicality. In-stead, they argue, all of the work in Lewis’s account is being done by the notion of self-ascription, yet this notion is not given an adequate explana-tion.

I can accept all of this. But the notion of first-person redundancy may be a distant cousin of the Lewisian notion of self-ascription. First-person redundancy involves a content that is about oneself, but judging that it obtains does not require an explicit representation of oneself. According to Lewis, all belief is self-ascription, for even the belief that grass is green amounts to the self-ascription of the property of being in a world where grass is green. I do not need to make any corresponding claim. My claims concern only a special category of egocentric mental representation indi-cated by (but not expressed by) the use of indexicals. So my account is compatible with a standard account of belief as a propositional attitude, an epistemic relation to a complete propositional content.

So why is there any connection with indexicality at all? The answer is that the references of indexicals such as ‘I’, ‘here’ and ‘now’ are governed by token-reflexive rules that coordinate closely with s-e relations. A token of ‘here’ stands for the place in which it is uttered. Because the thinking subject is the speaker of the utterance, when I utter ‘here’ I am located at the place referred to by ‘here’. So a use of ‘here’ connotes a relation be-tween the subject and the placed referred to by ‘here’. The same goes for other indexicals. The doctrine of the essential indexical should therefore be understood as the view that the mental states that are essential for ac-tion are coordinated with uses of indexicals. But indexicality per se has little or nothing to do with being essential for action. We could have done without indexicals; but we could not have done without the first-person redundant mental states whose presence they indicate.

Given the arguments thus far, we can rewrite the doctrine of the essen-tial indexical in an expanded form, as follows:

The Doctrine of the Essential Indexical*

There is a class of actions, CA (perhaps only the non god-like ac-tions, or perhaps all actions), such that no action in CA can be performed by an agent who lacks a first-person redundant mental state of the kind normally indicated by the use of an egocentric indexical.

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VIII. The Explanatory Gap

I believe that the notion of first-person redundancy is important for issues beyond the explanation of essential indexicality. I shall end with a brief discussion of one such issue, concerning what has come to be known as the explanatory gap. This refers to the apparent difficulty of explaining phenomenal consciousness in terms of physical processes, or of gaining knowledge of phenomenal consciousness just through knowledge of phys-ical processes, no matter how complete.19 To defend a materialist theory of the mental, one must explain, in materialistically acceptable terms, why there is an explanatory gap.

Thomas Nagel (1974) offered a possible explanation in terms of differ-ent perspectives on the world; for example neuroscience gives us a public, third-person description of brain activity, but the conscious subject experi-ences this same activity from a first-person point of view. We can use the notion of first-person redundancy to define a related notion of perspective that can be put to a similar use. Let a representational state be a first-per-son representation, or a representation from the first-person perspective, if and only if it is first-person redundant; otherwise let it be a third-person representation, or a representation from the third-person perspective. So, for example, when I see S standing in front of o (by seeing myself in a mirror, for example), I have a third-person representation R(S, o). It is the kind of representational state that others can share. But when I see o in front of me – or just o in front, as I might say – then I have a first-person representation, R({S}, o), of my relation to o. Only I can be in that state. Both experiences can represent the same state of affairs. But knowledge of the third-person representation does not suffice to give me knowledge of the first-person representation (or vice versa). There is no simple transla-tion procedure that automatically gets me from one to the other, for the difference between the first and third-person perspectives is a difference of epistemic perspective on the same content.

Now, suppose that all conscious experiences had representational con-tents, and that all were first-person redundant. This could be the case if the phenomenal character of any conscious experience represented an s-e relation – a view that I think is independently plausible.20 In that case, a conscious experience would give one a first-person representation of

19 The expression ‘explanatory gap’ was first coined by Joseph Levine (1983). The appar-ent gap between knowledge of the physical facts and knowledge of the phenomenological facts was of course argued for by Thomas Nagel (1974) and Frank Jackson (1982).20 I argue for this view for spatial experience in Prosser 2011 and for temporal experi-ence in Prosser forthcoming a: chapter 4. I hope to defend the more general view, that all conscious experiences are first-person redundant representations of s-e relations, in future work.

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a state of affairs that could also be represented from the third-person perspective. Thus Mary (the colour vision scientist from Jackson 1982, who knows all the physical facts but has never experienced colour) would know about all states of affairs from the third-person perspective. So she might know, for example, that Mary stands in an s-e relation, Rred, to o, where o is a red object. This would be third-person knowledge, accessible to everyone. But she would never have entertained this content from the first-person perspective. There is no reason why a person who has a third-person representation must have the ability to turn this into the equivalent first-person representation. And, if this line of thought is correct, then that is why Mary does not know what it is like to see something red until she has the experience. For to know what it is like to see something red requires either that one currently see something red, or that one is able to simulate the experience of something red, and Mary can do neither, prior to her first experience of red. For both of these would involve first-person redundant mental states, as described above. This, I suggest, is what Mary lacks, prior to her first experience of red.

Clearly more must be said to turn this brief outline into a complete ac-count. I leave this for further work.21

Department of PhilosophyEdgecliffe, The Scores

University of St AndrewsFife, KY16 9AR

[email protected]

21 I would like to thank audiences in St Andrews, Paris, Donostia [[[and London]]] for their helpful and encouraging comments. Special thanks go to Herman Cappelen for discussion and Michael Murez for his commentary at the PLM workshop in Donostia.

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